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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        function isRunYear(year) {
            var flag = false
            if ( year % 4 === 0 && year % 100 !==0 || year % 400 == 0) {
                flag = true
            }
            return flag
        }

        // function isRunYear(year) {
        //     if ( year % 4 === 0 && year % 100 !==0 || year % 400 == 0) {
        //         return true
        //     } else {
        //         return false
        //     }
        // }

        var res = isRunYear(2001)
        console.log(res);
    </script>
</body>
</html>